Dry season ecology of malaria vectors
- To seek direct evidence for each persistence strategy and evaluate its specific contribution to the persistence of malaria mosquitoes through the dry season.
- To understand the behavioral, physiological, and molecular mechanisms that underlie the strategies used by mosquitoes to persist throughout the dry season without surface waters.
- To develop new tools for tracking mosquitoes flying near the ground and at altitude and apply them to better understand disease transmission and the implications for disease control.
- Propose and evaluate novel disease control strategies based on the information obtained.
Even after two decades of intense control efforts, malaria remains important worldwide with an especially heavy burden in Africa. Outstanding gaps remain in our understanding of many aspects of vector biology, leading to spotty and unstable success in malaria control. The dry-season biology of malaria vectors is especially poorly understood despite its relevance to malaria control and growing concerns on health risks related to climate change in these areas. The means by which these mosquitoes and malaria persist in areas without surface water for three to eight months a year has been one of the long-standing questions in malariology as no stage of the vector is known to survive for over two months under such conditions. The hypotheses of dry season dormancy (aestivation) and of re-colonization via long-distance migration following the first rains have been proposed. If mosquitoes persist as non-reproductive, aestivating adults, they might be prime targets for vector control, especially if they also act as a reservoir for malaria (and other pathogens). Alternatively, if mosquitoes migrate from distant locations near permanent waters, identifying and targeting these sources can also improve malaria control. As efforts to eliminate and eradicate malaria intensify, understanding these issues to prevent reintroduction of the parasite and further depress transmission will be of importance.
Considering recolonization of Sahelian villages after the onset of rains, our results suggest that A. coluzzii persists through the long dry season via aestivation but A. gambiae and A. arabiensis re-colonize the area by wind-assisted long distance migration. Notably, our results demonstrate that A. coluzzii engages in windborne migration in the Sahel (starting from the mid-rainy season). The goal of this project is to fully resolve and understand the strategies used by the different vector species.